This invention relates to a process for preparing a hydrosilylation catalyst which is preferably used in synthesizing a silane coupling agent and, more particularly, to a process for preparing a hydrosilylation catalyst which is preferably used in synthesizing, by hydrosilylation reaction, a silane coupling agent of which demand is enlarged as an indispensable material in the development of ultrafasionable composite materials.
Heretofore, the following catalysts or processes (1) to (4) have been known as catalysts or processes which are used in synthesizing silane coupling agents by a hydrosilylation reaction. However, any of these catalysts or processes present problems as described hereinafter:
(1) as solution of chloroplatinic acid H.sub.2 PtCl.sub.6 6H.sub.2 O in isopropanol (see J.Amer.Chem.Soc., VOL.82, 3602(1960)).
This catalyst requires a considerably long period (generally called induction period) until it exhibits a steady catalytic activity. Further, it must be pretreated with a portion of a reaction reagent prior to the reaction.
(2) A platinum-beta-diketone complex (see Japanese Patent Publn. No.24947/1975).
When this catalyst is used, hydrosilylated products can be obtained in a relatively high yield by a reaction of allyl chloride and trichlorosilane as described in the Japanese Patent Publn. However, the reaction temperature is high, the reaction time is long, and the preparation of the catalyst takes a long time.
(3) A process wherein a choloroplatinic acid catalyst is used in the presence of phenothiazine, diphenylamine or the like (Japanese Patent Publn, No.29873/1981)
When this process is utilized, the induction period of the catalyst is reduced and it is possible to lower the reaction temperature. However, the yield of hydrosilylated objective products is low.
(4) A Reaction product of chloroplatinic acid and cyclohexanone (Japanese Patent publn. No.41132/1978)
When this catalyst is used, hydrosilylated products which are objective products are obtained in a relatively high yield. However, cyclohexanone reacts with silane compounds such as trichlorosilane.
It is therefore an object of the present invention to provide a process for preparing a hydrosilylation catalyst which meets the following requirements: (1) the preparation of the catalyst is simple; (2) the induction period can be shortened; (3) the catalyst or the auxiliary catalyst is not consumed, and (4) the reaction proceeds under mild conditions and the silane coupling agent can be obtained in a high yield.